Pan-Roasted Swordfish with Tarragon-Mustard Sauce

INGREDIENTS

• 1 tablespoon unsalted butter
• 2 tablespoons coarsley chopped fresh tarragon
• 1/8 cup finely chopped shallot
• 1/2 cup dry vermouth
• 4 tablespoons unsalted butter, softened
• 1/2 tablespoon olive oil
• 1/2 to 1 tablespoon Dijon mustard (smooth, not grainy)
• one 1-inch-thick swordfish steak (about 1 lb.)
• Sea salt
• fresh cracked black pepper